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Date: Thu, 1 May 2008 11:58:26 -0400
From: Christoph Hellwig <hch@infradead.org>
To: Michael Buesch <mb@bu3sch.de>
Cc: Christoph Hellwig <hch@infradead.org>,
       Jesse Barnes <jbarnes@virtuousgeek.org>,
       John Linville <linville@tuxdriver.com>,
       Andi Kleen <andi@firstfloor.org>, David Miller <davem@davemloft.net>,
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       bcm43xx-dev@lists.berlios.de, linux-wireless@vger.kernel.org,
       linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 0/3] Add API for weak DMA masks
Message-ID: <20080501155826.GA11188@infradead.org>
References: <200805011638.15910.mb@bu3sch.de> <200805011742.05302.mb@bu3sch.de> <20080501154358.GA3318@infradead.org> <200805011747.27469.mb@bu3sch.de>
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On Thu, May 01, 2008 at 05:47:26PM +0200, Michael Buesch wrote:
> We've discussed that and this behaviour is not acceptable, as the driver
> must know about a possible fallback in case it can do 32bit DMA
> more efficiently than 64bit DMA, for example.

That's what we have dma_get_required_mask() for.  See
Documentation/DMA-API.txt.